The largest lava cave system ever explored in Southeast Asia in Vietnam's Central Highlands province of Dak Nong is now open to tourists, with a Ho Chi Minh City-based company organizing tours to the place.

Thế Hệ Trẻ travel company organizes visits to a tube-shaped cave 594.4 meters long and another cave with beautiful old trees and a natural hole that allows the sun to shine through.

Vietnamese geologists and members of the Japanese Caving Association started surveying the Chu Bluk system in 2007.

Late last year they announced that it is the longest lava cave system in the region, stretching around 25 kilometers and with dozens of caves.

Scientists said the system is a unique vestige of a formative volcanic eruption millions of years ago.

They have only surveyed three caves fully.

But tourists going on the cave tour can also see other local attractions, including performances of the gong and other music instruments by the M’Nong ethnic people.

A two-night tour costs VND3,072,000 (US$140) per person, according to the company’s website.